The present invention concerns a valve stem system and, in particular, a valve stem system which is manipulator operable and designed for use on flowlines in submerged oil and/or gas production systems. Valves used in such systems are not easily repaired or replaced. Failure mode analysis which has been conducted indicates that the most likely failure would arise in the valve stem packing and, consequently, to improve the reliability of the system in which the valves are used it is desirable to eliminate dependency upon the valve stem packing to provide the required seal.